Yaas may become a very severe cyclonic storm: IMD

#GS3 #DISASTER MANAGEMENT #CYCLONES 

Context:

  • Cyclone Yaas may intensify into a “very severe cyclonic storm” and cross the Odisha and West Bengal coasts on May 26, reported by India Meteorological Department (IMD)
  • A low pressure area developed over the east-central Bay of Bengal and the besides north Andaman Sea on Saturday.

Current ongoing report:

  • The low area is extremely likely to concentrate into a depression over the east central Bay of Bengal by tomorrow, May 23 morning. it's very likely to maneuver north-northwestwards, intensify into a cyclonic storm by 24th May and further into a really severe cyclonic storm during the next 24 hours,” the Meteorological department said.

    The cyclonic system would still move north-northwestwards, intensify further and reach the north Bay of Bengal near West Bengal and therefore the adjoining north Odisha and Bangladesh coasts by the morning of May 26
Categories of Tropical Cyclones - destruction

BIASA BASICS 

what are tropical cyclones?

Cyclonic disturbances are rapid weather systems, which include weather depressions, deep depressions, and tropical cyclones (of severe, very severe, extremely severe, and super cyclonic storms counting on their intensity).

  • Tropical cyclones are violent storms that develop  over oceans in tropical areas and give way to the coastal areas bringing about large-scale destruction caused by violent winds, very heavy rainfall, and storm surges.
  • Cyclones create a whirl within the atmosphere with very strong winds circulating around it during a n anti-clockwise direction within the northern hemisphere and in a clockwise direction within the southern hemisphere.
  • The pressure gradient falls towards the middle from all directions and thus winds attempt to converge towards the middle from all directions. The air blows inwards in an anticlockwise direction within the hemisphere and clockwise within the hemisphere .

Conditions for formation of Cyclones

The conditions suitable for the formation and intensification of tropical storms are:

  1. A consistent source of warmth as tropical cyclones are thermally induced low-pressure systems.
  2. Large sea surface with a temperature above 27° C which is feasible only during the late summers i.e. September, October, and November
  3. Presence of the Coriolis force .
  4. Small variations within the vertical wind speed.
  5. A pre-existing weak low-pressure area or low-level-cyclonic circulation;
  6. Upper divergence above the ocean level system.

Structure of Tropical Cyclone

The structure of a Tropical Cyclone is usually a huge cumulonimbus with rapidly rising air spiraling upwards at the margins of the attention . an eye fixed may be a region of calm with subsiding air. round the eye is that the Eyewall, where strong spiraling winds ascends and therefore the height can reach up to the tropopause.

Tropical cyclones are formed by the subsequent parts:

Eye:  

The eye is that the center of cyclones which is characterized by a relaxed area, sinking, and lightweight wind. the attention is that the calmest a part of the Cyclone structure.

Conservation of momentum and force are the explanations behind its formation.

Eyewall:

A band round the eye of the best wind speed, where clouds reach the very best and precipitation is that the heaviest. The heaviest wind damage occurs where a hurricane’s eyewall passes over land.

Rain bands:

Curved bands of clouds and thunderstorms that trail faraway from the eyewall during a spiral fashion. These bands are capable of manufacturing heavy bursts of rain and wind. Sometimes gaps are found between spiral rain bands, where no impact (wind or rain) of cyclones are found.

How does the formation of tropical cyclones takes place:

  • As mentioned within the conditions, air temperature above 27° C with an abundant and turbulent transfer of water vapour to the overlying atmosphere (air) by evaporation is required for the formation of Cyclones, which is facilitated by direct insolation.
  • As the low-pressure area is made over sea pockets and high on the encompassing areas, air starts to be due the high-pressure area to low-pressure pockets.
  • The Coriolis force causes the wind to spiral around a low-pressure area. because the presence of Coriolis force is negligible within the equatorial belt between 5 degrees north and 5 degrees south latitudes, hence cyclonic systems don't develop during this region.
  • Heated sea surface starts to heat the air over that resulting in air moving up and faraway from the ocean surface thanks to convection, it leaves less air near the surface. Cool Air from the encompassing areas rushes towards the empty area to fill it, which after reaching there gets heated and picks moisture and starts rising upwards. It creates the cycle of air occupation and up.
Cyclone Structure
  • As the moist air rises up, it starts cooling with the altitude (temperature falls with the height), and therefore the process of condensation starts. It leads to the discharge of the heat of transformation of condensation. The heat of transformation of condensation is what drives the storm and results in the formation of clouds.
  • The energy that intensifies the storm, comes from the condensation process within the towering cumulonimbus clouds, surrounding the middle of the storm (Eye).
  • With the increasing altitude, the air cools right down to an extent at tropopause where it fails to rise any longer and starts to diverge outside horizontally.
  • The whole system of clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the ocean surface. because the storm system rotates faster and faster, an eye fixed forms within the center.
  • A mature tropical cyclone is characterized by the strong spirally circulating wind round the center, called the attention . The diameter of the circulating system can vary between 150 and 250 km.
  • Rain bands regions with cumulonimbus clouds are created, facilitating intense rainfall therein region. Cloud formation is dense at the middle and density decrease towards the surface .

Conditions that slow or end Cyclones

  • With endless supply of moisture from the ocean , the storm is further strengthened. On reaching the land the moisture supply is stop and therefore the storm dissipates. The place where a tropical cyclone crosses the coast is named the landfall of the cyclone.
  • Another condition that slowdown or ends a Cyclone is when dry, cool air is suddenly present within the system, which reduces the likelihood of convection to stay the storm going.

Government Initiatives:

  • Government is conducting out a National Cyclone Risk Mitigation Project (NCRMP) with the help of the World Bank to advance cyclone forecasting, tracking, and warning systems in India
  • Government is also preparing the Integrated Coastal Zone Management Project (ICZMP) to improve national capacity for the conduction of comprehensive coastal management in India.
  • Government also separated Structural(includes construction) and non-structural measures for effective disaster management of cyclones

Solutions:

  • The government should consider the NDMA Guidelines for the management of cyclones:
  • Ensemble Warning System(EWS): Establish EWS involving observations, predictions, warnings, and customized local level advice for decision-makers (national, state, district level) to manage the impact of the cyclone (Read more about EWS)
  • Commissioning of Aircraft Probing of Cyclone (APC): Guidelines calls for the combination of manned and Unmanned Aerial Vehicles (UAV) for critical observational data gaps.
  • Cyclone Disaster Management Information System (CDMIS): Establishing a comprehensive department for coverage of all management information and provide online services to the departments of Disaster management.
  • Specifying the roles and responsibilities in institutionalizing Cyclone risk mitigation with Developmental planning.
  • Community-Based Disaster Management (CBDM): Guidelines asked to launch such activities in all villages of the 84 districts vulnerable to cyclones.

 

SOURCE: THE HINDU 

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